Maruo 

 Then the wave resistance can be written as 



R =- Pg — 7c 



where 



exp 



7 — - sec 



X.77 



sin (7 sec ^) sec^6'd0 



(77) 



2 A, 



(78) 



The ratio k can be chosen in such a way that the resulting wave resistance be- 

 comes minimum. If the volume of the submerged part is kept constant, it is 

 merely given by the equation 



BR 



dk 



(79) 



Calculation has been carried out for cases of l/i = 4 and 5. Models for tank 

 experiment were prepared as shown in Fig. 14. Figure 15 shows some of the 

 results of the experiment together with the computed curves. The designed 

 speed at which the relation Eq. (79) holds is indicated by the arrow. As the ex- 

 perimental value is the residuary resistance coefficient, some difference exists 

 between the experimental curves and the theoretical wave resistance coefficient. 

 However, the general feature of the curves is similar. There are also shown 

 theoretical curves of wave resistance coefficient when the submerged body, the 

 Rankine ovoid, moves alone under the water surface, and one can observe how 

 the wave resistance is reduced by the interference between two parts. 



Figure 14 



Kotik calculated the value of minimum wave resistance of elementary ships 

 at Froude number 0.4. For a wall-sided ship of draft length ratio 0.1, the wave 

 resistance coefficient defined by 



1044 



